CN110845471A - Process for synthesizing photoinitiator 2,4-diethyl thioxanthone by one-pot method - Google Patents
Process for synthesizing photoinitiator 2,4-diethyl thioxanthone by one-pot method Download PDFInfo
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- CN110845471A CN110845471A CN201911139133.6A CN201911139133A CN110845471A CN 110845471 A CN110845471 A CN 110845471A CN 201911139133 A CN201911139133 A CN 201911139133A CN 110845471 A CN110845471 A CN 110845471A
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- acid
- diethyl thioxanthone
- dithiosalicylic
- concentrated sulfuric
- cocatalyst
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D335/00—Heterocyclic compounds containing six-membered rings having one sulfur atom as the only ring hetero atom
- C07D335/04—Heterocyclic compounds containing six-membered rings having one sulfur atom as the only ring hetero atom condensed with carbocyclic rings or ring systems
- C07D335/10—Dibenzothiopyrans; Hydrogenated dibenzothiopyrans
- C07D335/12—Thioxanthenes
- C07D335/14—Thioxanthenes with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached in position 9
- C07D335/16—Oxygen atoms, e.g. thioxanthones
Abstract
A process for synthesizing 2,4-diethyl thioxanthone serving as a photoinitiator by a one-pot method. The invention belongs to the field of fine chemical engineering, and particularly relates to a process for synthesizing 2,4-diethyl thioxanthone by a one-pot method. Concretely, thiosalicylic acid or dithiosalicylic acid and 1, 3-diethylbenzene are used as raw materials, concentrated sulfuric acid is used as a catalyst and a solvent, and condensation reaction is carried out for 4-8 hours at the temperature of 0-70 ℃ under the action of a cocatalyst. After-treatment processes such as condensation, extraction, concentration, recrystallization and the like are integrated in the same reaction device to be completed, and the obtained product is filtered and dried to obtain the high-purity 2,4-diethyl thioxanthone. The method has the advantages of good selectivity, low reaction temperature, short reaction time, high yield, simple and convenient operation, high single kettle efficiency and the like, reduces equipment investment, reduces energy consumption, operation intensity and production cost, and is suitable for industrial production.
Description
Technical Field
The invention belongs to the field of fine chemical engineering, and particularly relates to a process for synthesizing photoinitiator 2,4-diethyl thioxanthone by a one-pot method, which takes thiosalicylic acid or dithiosalicylic acid and 1, 3-diethylbenzene as raw materials, concentrated sulfuric acid as a catalyst and a solvent, and concentrates the processes of condensation, extraction, concentration, recrystallization and the like in the same reaction device under the action of a cocatalyst, and the obtained product is filtered and dried to finally obtain the high-purity 2,4-diethyl thioxanthone. The method has the advantages of good selectivity, low reaction temperature, short reaction time, high yield, simple and convenient operation, high single kettle efficiency and the like, reduces equipment investment, and reduces operation intensity and production cost.
Background
Thioxanthone (also called thioxanthone) compounds are often used as photoinitiators or activators for radiation-curable or radiation-crosslinkable unsaturated compounds, and have wide application in the fields of photocuring inks, coatings and adhesives. Among them, 2, 4-diethylthioxanthone (English)The name 2,4-Diethyl thiophanthone, abbreviated as DETX) is the most common one. DETX, molecular formula: c17H16OS, molecular weight: 268.37, CAS registry number: [82799-44-8]As pale yellow crystalline powder, melting point: the temperature is 70-71 ℃, and the UV curing coating is mainly applied to UV curing coatings and printing ink.
Generally, thioxanthones and derivatives thereof are prepared by the substitution and condensation of thiosalicylic acid or dithiosalicylic acid with unsubstituted or substituted aromatic compounds in a sulfuric acid medium (see J.org.chem.1959,24, 1914-. The production process of 2, 4-diethylthioxanthone basically follows the above-mentioned technological route, and still uses concentrated sulfuric acid as solvent and catalyst (J.chem.Soc.1911,99,645, JPS 57163377 and CN 102250060 are all adopted in said process), and uses thiosalicylic acid or dithiosalicylic acid and 1, 3-diethylbenzene to make preparation. The process has the advantages of high reaction temperature, more side reactions (especially some sulfonated aromatic compounds), impure colors in product appearance, poor appearance such as trace red impurities in product appearance, high post-treatment difficulty, multiple treatment, product distillation and other steps, high working strength, and low equipment utilization rate and labor efficiency.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: overcomes the defects in the prior art, and provides a process for synthesizing 2,4-diethyl thioxanthone by a one-pot method, which has the advantages of high yield, mild reaction conditions, good product quality and simple and convenient operation. The process can improve the separation yield of the target product.
The process of the present invention, which is another object of the present invention, is not only low in reaction temperature, low in energy consumption and low in cost, but also can improve the quality of the objective product with minimal or no residual organic or inorganic by-products and good appearance.
The process can complete several steps in one reactor, and has simple operation and high yield and/or improved product quality.
In order to solve the technical problems, the invention adopts the following typical technical scheme:
the method for preparing 2,4-diethyl thioxanthone provided by the invention is to perform condensation reaction for 4-8 hours at the temperature of 0-70 ℃ by taking thiosalicylic acid or dithiosalicylic acid and 1, 3-diethylbenzene as raw materials and concentrated sulfuric acid as a solvent and a catalyst in the presence of a cocatalyst. Preferably 50-65 ℃ for 5-7 hours. The molar ratio of the 1, 3-diethylbenzene to the thiosalicylic acid or the dithiosalicylic acid is 1.0-5.0: 1, preferably 1.5-4.0: 1, the cocatalyst is used in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total reaction mixture.
After the reaction is completed, the product can be purified by the following method, and the target product 2,4-diethyl thioxanthone can be obtained with high yield by adding an organic solvent into the product for extraction, washing, concentrating and finally recrystallizing.
The method may further be described as follows:
(1) condensation reaction;
(2) and (2) adding an extraction solvent and water into the mixture obtained in the step (1), uniformly stirring, and then carrying out phase separation, washing, concentration and desolventizing, and recrystallization to obtain the product.
Step (1) is to add thiosalicylic acid or dithiosalicylic acid, 1, 3-diethylbenzene and a cocatalyst into concentrated sulfuric acid to carry out condensation reaction at a certain temperature.
In the step (1), the using amount of the concentrated sulfuric acid is 5-200 ml of concentrated sulfuric acid per mole of thiosalicylic acid or dithiosalicylic acid, and the appropriate amount is 20-100 ml of concentrated sulfuric acid per mole of thiosalicylic acid or dithiosalicylic acid.
In the step (1), the molar ratio of 1, 3-diethylbenzene to thiosalicylic acid (or equivalent dithiosalicylic acid) is 1.0-5.0: 1, preferably in a molar ratio of 1.0 to 5.0:1, preferably 1.5 to 4.0: 1.
the promoter used in step (1) is a strong acidic substance, including but not limited to: trifluoromethanesulfonic anhydride, polyphosphoric acid, phosphorus pentoxide, and the like.
The amount of the cocatalyst used in step (1) is 0.5 to 10% (wt%), preferably 1 to 10%, of the total reaction mixture.
The reaction time in the step (1) is 4-7 hours.
The reaction temperature in the step (1) is 0-70 ℃, and the preferable reaction temperature is 50-65 ℃.
The step (2) is reaction post-treatment: after the reaction is completed, cooling to room temperature, adding an extraction solvent and water, stirring, carrying out phase separation, washing an organic phase with water and brine, drying, filtering and concentrating. The obtained crude product is recrystallized once to obtain a finished product.
In the step (2), the solvent used for extraction is aliphatic hydrocarbon, such as n-hexane, n-heptane, n-octane, petroleum ether and the like; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, methylcyclohexane, and the like; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, n-propylbenzene, isopropylbenzene, xylene, diethylbenzene and the like; halogenated alkanes and halogenated aromatic hydrocarbons such as dichloromethane, 1, 2-dichloroethane, 1-dichloroethane, chloroform, carbon tetrachloride, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, etc.; ethers such as diethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl tert-ether, ethyl n-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.; esters such as ethyl formate, propyl formate, isopropyl formate, butyl formate, isobutyl formate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, benzyl formate, benzyl acetate, and the like. Aliphatic hydrocarbons and aromatic hydrocarbons are preferred.
In the step (2), the solvent used for recrystallization is water, alcohols, ethers, such as methanol, ethanol, n-propanol, iso-alcohol, n-butanol, iso-butanol, n-pentanol, iso-pentanol, neopentyl alcohol, cyclohexanol, cycloheptanol, diethyl ether, methyl tert-ether, isopropyl ether, methyl ethyl ether, methyl n-butyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like, and can be used alone or in combination.
Compared with the prior art CN 102250060, the method for synthesizing 2,4-diethyl thioxanthone has the advantages of high yield, mild reaction conditions, high single-kettle efficiency, less impurities, simple post-treatment, no distillation step, good product quality and less waste, so the production cost and the raw material cost are greatly reduced, and the method is a production method suitable for industrialization.
Detailed description of the preferred embodiments
The present invention is further illustrated by the following examples, which are provided by way of illustration only and are not intended to limit the scope of the invention.
Example one
40 ml of concentrated sulfuric acid, 100 g of dithiosalicylic acid and 8 g of polyphosphoric acid are added into a 500ml four-mouth reaction bottle, the mixture is cooled to below 0 ℃ by a ice salt bath under stirring, 100 g of 1, 3-diethylbenzene is dropwise added, and the reaction temperature is controlled to be not more than 5 ℃. After the addition, the ice salt bath was removed, the temperature was naturally raised to room temperature, and the reaction was continued for 1 hour. And (3) changing the reaction kettle into an oil bath, slowly heating to 65 ℃, reacting for 5 hours at 65 ℃, and tracking the reaction by HPLC until the dithio-salicylic acid completely reacts. Cooling a reaction product, adding 90 g of 1, 3-diethylbenzene and 60 g of water, stirring for half an hour, standing for phase separation, carrying out alkali washing and water washing on an organic phase, concentrating, cooling to 5 ℃, standing overnight, filtering the next day, washing a filter cake with a small amount of glacial ethanol, and drying in vacuum to obtain 150 g of bright yellow crystalline powder, namely DETX finished product, wherein the yield is 90.2%, the melting point is 71-72 ℃, and the purity of the product is 99.6% by HPLC (high performance liquid chromatography).
Example two
40 ml of concentrated sulfuric acid, 2 g of phosphorus pentoxide and 16 g of methanesulfonic acid are sequentially added into a 500ml four-mouth reaction bottle, stirred uniformly, then 100 g of thiosalicylic acid is added, the mixture is cooled to below 0 ℃ by a ice salt bath under stirring, 100 g of 1, 3-diethylbenzene is dropwise added, and the reaction temperature is controlled to be not more than 5 ℃. After the addition, the ice salt bath was removed, the temperature was naturally raised to room temperature, and the reaction was continued for 1 hour. Changing to oil bath, slowly heating to 65 ℃, reacting for 5 hours at 65 ℃, tracing the reaction by HPLC, cooling after the dithio-salicylic acid completely reacts, adding 90 g of toluene and 60 g of water, stirring for half an hour, standing for phase separation, and carrying out alkali washing, water washing and concentration on an organic phase. Adding anhydrous methanol and activated carbon into residues, heating to 45 ℃, stirring for half an hour, filtering while the residues are hot, naturally cooling mother liquor to room temperature, then cooling to 5 ℃, standing overnight, filtering the mother liquor the next day, washing a filter cake with a small amount of glacial methanol, and drying in vacuum to obtain 155.4 g of bright yellow crystalline powder, wherein the yield is 89.2%, the melting point is 71-72 ℃, and the purity of a product is 99.7% by HPLC (high performance liquid chromatography).
Claims (8)
1. A one-pot synthesis process of 2,4-diethyl thioxanthone is characterized in that thiosalicylic acid or dithiosalicylic acid and 1, 3-diethylbenzene are used as raw materials, concentrated sulfuric acid is used as a solvent and a strong acid substance catalyst in the presence of a cocatalyst, and condensation reaction is carried out for 4-8 hours at the temperature of 0-70 ℃; the molar ratio of the 1, 3-diethylbenzene to the thiosalicylic acid or the dithiosalicylic acid is 1.0-5.0, and the use weight of the cocatalyst is 0.5-10% of the weight of the total reaction mixture.
2. The process as claimed in claim 1, wherein the cocatalyst is used in an amount of 1 to 5% by weight based on the total reaction mixture.
3. The process as claimed in claim 1, wherein the reaction temperature is 50-65 ℃.
4. The process according to claim 1, wherein the strongly acidic substance is trifluoromethanesulfonic anhydride, polyphosphoric acid, or phosphorus pentoxide.
5. The process according to claim 1, wherein the concentrated sulfuric acid is used in an amount of 5 to 200ml per mole of thiosalicylic acid or dithiosalicylic acid.
6. The process according to claim 5, wherein the concentrated sulfuric acid is used in an amount of 20 to 100ml per mol of thiosalicylic acid or dithiosalicylic acid.
7. The process as claimed in claim 1,2, 3, 4, 5 or 6, wherein the product is cooled to room temperature, organic extraction is added, the organic phase is washed with water and brine respectively, filtration and concentration are carried out, and the crude product obtained is recrystallized from an organic solvent.
8. The process as claimed in claim 7, wherein the organic solvent used for extraction is aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon, halogenated alkane and halogenated aromatic hydrocarbon, or ether or ester organic solvent.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112778269A (en) * | 2020-12-30 | 2021-05-11 | 山东久日化学科技有限公司 | Preparation method of thioxanthone photoinitiator |
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| GB1001824A (en) * | 1960-08-26 | 1965-08-18 | Sandoz Ag | Homothiaxanthone |
| US4450279A (en) * | 1981-03-16 | 1984-05-22 | Nippon, Kayaku, Kabushiki, Kaisha | Dialkylthioxanthones |
| US5712401A (en) * | 1996-04-29 | 1998-01-27 | First Chemical Corporation | Processes for preparing thioxanthone and derivatives thereof |
| CN1461302A (en) * | 2000-11-15 | 2003-12-10 | 波隆有限公司 | Friedel-crafts process for the preparation of thioxanthones |
| US20040059133A1 (en) * | 2002-07-13 | 2004-03-25 | Great Lakes (Uk) Limited | Process for the production of substituted thioxanthones |
| CN102250060A (en) * | 2011-05-27 | 2011-11-23 | 连云港升南化学有限公司 | Preparation method of 2,4-diethyl thioxanthone |
| CN108424409A (en) * | 2018-03-16 | 2018-08-21 | 吉安市东庆精细化工有限公司 | A kind of method of solid acid catalysis synthesis photoinitiator 2,4- diethyl thioxanthones |
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2019
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Patent Citations (7)
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| GB1001824A (en) * | 1960-08-26 | 1965-08-18 | Sandoz Ag | Homothiaxanthone |
| US4450279A (en) * | 1981-03-16 | 1984-05-22 | Nippon, Kayaku, Kabushiki, Kaisha | Dialkylthioxanthones |
| US5712401A (en) * | 1996-04-29 | 1998-01-27 | First Chemical Corporation | Processes for preparing thioxanthone and derivatives thereof |
| CN1461302A (en) * | 2000-11-15 | 2003-12-10 | 波隆有限公司 | Friedel-crafts process for the preparation of thioxanthones |
| US20040059133A1 (en) * | 2002-07-13 | 2004-03-25 | Great Lakes (Uk) Limited | Process for the production of substituted thioxanthones |
| CN102250060A (en) * | 2011-05-27 | 2011-11-23 | 连云港升南化学有限公司 | Preparation method of 2,4-diethyl thioxanthone |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112778269A (en) * | 2020-12-30 | 2021-05-11 | 山东久日化学科技有限公司 | Preparation method of thioxanthone photoinitiator |
| CN112778269B (en) * | 2020-12-30 | 2022-09-02 | 山东久日化学科技有限公司 | Preparation method of thioxanthone photoinitiator |
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